Is NS Square needed or is it a vanity project?

I have no issue with large scale building projects that the Government undertakes. Upgrades, face lifts etc. are all part and parcel of keeping a nation relevant and vibrant. However, given that large scale building projects are costly and funded by public funds, there needs to be accountability and follow up. The Straits Times (ST) recently reported that The Float @ Marina Bay will be replaced by the construction of a new and permanent NS Square which is targeted to be completed and handed over by the third quarter of 2025. While the ST report did not mention the costs that are projected to be incurred by this new permanent structure, I can only imagine that it isn’t going to come cheap.
Until late 2017, The Float @ Marina Bay was never meant to be a permanent structure. It was only constructed as a stop gap measure to hold national events such as the National Day Parade (NDP) while the Sports Hub (the former National Stadium) was being constructed. Why the change? Were there any Parliamentary debates on this?
Going back to 2008 when it was first announced that the National Stadium was to be torn down and replaced with the Sports Hub, it was always envisaged that the NDPs were to be held there. Not only is the NDP now no longer held there, the structure that was erected as a stop gap measure is now going to become permanent and will be holding the next few NDPs. Why?
I am not asking these questions out of negativity. I am asking them because these projects cost huge amounts of public money and should only be spent after due discourse and approval processes in Parliament. These are public monies that should not be “wasted” so to speak if our elected representatives in government do not deem them necessary. But were the MPs even asked?

1. Why is the NDP no longer to be held in the Sports Hub when part of the reason cited for the rebuilding of the National Stadium was to create a design that had “the flexibility and scalability for hosting large-scale events, including the National Day Parade”?
2. What is the financial justification for building NS Square? What is the cost/benefit analysis? What else will it be used for apart from the NDPs in 2020 and 2021?

There is nothing wrong with rebuilding and refurbishing. It is only questionable if it is not properly justified. We do not need a vanity project. We need an actual cost/benefit analysis.